Been having a few issues lately with contaminates fouling plugs and oil burn.
I noticed my PCV valve is connected directly to the intake manifold, bypassing the air filter.
Is this likely to be an issue by re circulating contaminates?

 

You have not stated a year but normally it goes into the base of the Q-Jet. Nothing to do with the air filter.

 

The PCV is usually connected to the base of the carburetor though the intake will work as well. It does not go through the air filter. Idea was to burn gasses coming from the crankcase. Older motors, pre 67 or there abouts used to just dump crankcase gasses out a tube (Fords).

There is a hose which goes from the other valve cover to the air cleaner, on the inside of the filter. This one usually has a screen filter.

If you're burning oil, maybe do a compression test to get an idea of that state of your rings. Could also be worn valve guides or leaking valve seals. Is the PCV valve clean, parts move freely inside?

 

patto,

When pollution control came into effect in the early seventies, the usual way to burn these internal "fumes" was to suck them into the inlet manifold either directly or through an inlet on the base of the carb. But, where did that air and fumes come from?

The usual way on a V8 was to have an INLET on one rocker cover and the EXHAUST on the other. So, ambient air is sucked into the air filter because of lower pressure in the air cleaner of a running engine.

Most went via the carburettor into the engine, but a small amount, especially with the throttle closed, went via a rubber hose to the rocker cover WITHOUT the PCV valve. This FILTERED air went through the engine and picked up combustible oil and petrol fumes ( if any ) in the crankcase and via the suction of the fitting in the inlet manifold, it was drawn through the PCV valve on the other rocker cover and into the inlet manifold below the throttle valves and burnt.

(Note that some engines, especially those with aftermarket ACs, don't have this rubber hose from the AC to the rocker cover but instead just have a push in "breather" to allow unfiltered air to get into the engine.)

The former method is how GM ( and others ) designed it and it works pretty well. The problems you're having are more likely to be correctly diagnosed by following BBCorv's advice.

Good luck!

Regards from Down Under

aussiejohn

 

Thanks for this, I have been burning oil on this 290 hp crate motor since the warranty ran out. When we did an initial inspection the seals were broken so we were advised to have the stems? re machined as they were too long which was done but still the burn and now the solid contaminates across the spark plugs twice in 3 months.(PS the plugs are very very hard to get at and I am thinking of replacing the extractors with the original ram horns. To make matters harder this is a right hand drive).
I have re conditioned Vortex heads which I am planning to put on, hoped I might have found an easy fix with the PCV.
This is a 1980 C3.